Researchers found young men who scored lowest on intelligence tests were more likely to commit suicide in later years.
In particular, young men who scored the worst on tests of logic at age 18 were two to three times more likely to commit suicide during middle age than those with the best scores.
Researchers say the link between intelligence and suicide risk is unclear. But these results suggest that intellectual capacity in early adulthood is strongly related to the subsequent risk of suicide in young men.
Low IQ, Suicide Risk
In the study, which appears in the Jan. 22 issue of the British Medical Journal, researchers examined the association between intelligence test scores in men at age 18 and the risk of suicide in later years.
They analyzed the results of four intelligence tests covering logic, language, spatial, and technical skills given to nearly a million Swedish men from 1968-1994. The men were then followed for up to 26 years.
Better test performance was associated with a lower risk of suicide. This relationship was particularly strong in regard to logic abilities. Men who scored the best on this test were two to three times less likely to have committed suicide during the follow-up period compared with the men who had the worst scores.
Researchers say more studies are needed to investigate the relationship between intelligence and suicide risk, as previous studies have had conflicting results.
But they say one possible explanation is that influences in early childhood may increase a person's susceptibility to mental illness and, therefore, suicide. Another explanation may be that people who have a harder time solving problems in times of crisis may be more prone to suicide than others.